TY - JOUR
T1 - Geometries of edge and mixed dislocations in bcc Fe from first-principles calculations
AU - Fellinger, Michael R.
AU - Tan, Anne Marie Z.
AU - Hector, Louis G.
AU - Trinkle, Dallas R.
N1 - Funding Information:
This material is based upon work supported by the Department of Energy National Energy Technology Laboratory under Award Number DE-EE0005976. Additional support for this work was provided by NSF/DMR Grant No. 1410596. This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof. The research was performed using computational resources provided by the National Energy Research Scientific Computing Center. Additional computational resources were sponsored by the Department of Energy's Office of Energy Efficiency and Renewable Energy and located at the National Renewable Energy Laboratory, the General Motors High Performance Computing Center, and the Golub cluster maintained and operated by the Computational Science and Engineering Program at the University of Illinois.
Publisher Copyright:
© 2018 American Physical Society.
PY - 2018/11/26
Y1 - 2018/11/26
N2 - We use density functional theory (DFT) to compute the core structures of a0[100](010) edge, a0[100](011) edge, a0/2[111](110) edge, and a0/2[111](110)71-mixed dislocations in body-centered cubic (bcc) Fe. The calculations are performed using flexible boundary conditions (FBC), which effectively allow the dislocations to relax as isolated defects by coupling the DFT core to an infinite harmonic lattice through the lattice Green function (LGF). We use the LGFs of the dislocated geometries in contrast to most previous FBC-based dislocation calculations that use the LGF of the bulk crystal. The dislocation LGFs account for changes in the topology of the crystal in the core as well as local strain throughout the crystal lattice. A simple bulklike approximation for the force constants in a dislocated geometry leads to dislocation LGFs that optimize the core structures of the a0[100](010) edge, a0[100](011) edge, and a0/2[111](110)71-mixed dislocations. This approximation fails for the a0/2[111](110) dislocation, however, so in this case we derive the LGF from more accurate force constants computed using a Gaussian approximation potential. The standard deviations of the dislocation Nye tensor distributions quantify the widths of the dislocation cores. The relaxed cores are compact, and the local magnetic moments on the Fe atoms closely follow the volumetric strain distributions in the cores. We also compute the core structures of these dislocations using eight different classical interatomic potentials, and quantify symmetry differences between the cores using the Fourier coefficients of their Nye tensor distributions. Most of the core structures computed using the classical potentials agree well with the DFT results. The DFT core geometries provide benchmarking for classical potential studies of work-hardening, as well as substitutional and interstitial sites for computing solute-dislocation interactions that serve as inputs for mesoscale models of solute strengthening and solute diffusion near dislocations.
AB - We use density functional theory (DFT) to compute the core structures of a0[100](010) edge, a0[100](011) edge, a0/2[111](110) edge, and a0/2[111](110)71-mixed dislocations in body-centered cubic (bcc) Fe. The calculations are performed using flexible boundary conditions (FBC), which effectively allow the dislocations to relax as isolated defects by coupling the DFT core to an infinite harmonic lattice through the lattice Green function (LGF). We use the LGFs of the dislocated geometries in contrast to most previous FBC-based dislocation calculations that use the LGF of the bulk crystal. The dislocation LGFs account for changes in the topology of the crystal in the core as well as local strain throughout the crystal lattice. A simple bulklike approximation for the force constants in a dislocated geometry leads to dislocation LGFs that optimize the core structures of the a0[100](010) edge, a0[100](011) edge, and a0/2[111](110)71-mixed dislocations. This approximation fails for the a0/2[111](110) dislocation, however, so in this case we derive the LGF from more accurate force constants computed using a Gaussian approximation potential. The standard deviations of the dislocation Nye tensor distributions quantify the widths of the dislocation cores. The relaxed cores are compact, and the local magnetic moments on the Fe atoms closely follow the volumetric strain distributions in the cores. We also compute the core structures of these dislocations using eight different classical interatomic potentials, and quantify symmetry differences between the cores using the Fourier coefficients of their Nye tensor distributions. Most of the core structures computed using the classical potentials agree well with the DFT results. The DFT core geometries provide benchmarking for classical potential studies of work-hardening, as well as substitutional and interstitial sites for computing solute-dislocation interactions that serve as inputs for mesoscale models of solute strengthening and solute diffusion near dislocations.
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U2 - 10.1103/PhysRevMaterials.2.113605
DO - 10.1103/PhysRevMaterials.2.113605
M3 - Article
AN - SCOPUS:85060640148
SN - 2475-9953
VL - 2
JO - Physical Review Materials
JF - Physical Review Materials
IS - 11
M1 - 113605
ER -